Dyeing articles composed of acrylonitrile polymers



Patented Dec. 2, 1947 DYEING ARTICLES COMPOSED OF ACRYLONITRILE POLYMERS Frank Baldwin Moody, Pennsvllle, N. J aasignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application May 4, 1945, Serial No. 592,067

(Cl. H6)

4 Claims.

This invention is concerned with the art of dyeing and relates in particular to a new and effective process of dyeing articles composed of acrylonitrile polymers.

Articles composed of polyacrylonitrile, i. e. polymerized vinyl cyanide [(CH:=CHCN)=] and other acrylonitrile polymers in which at least 85% by weight of the polymer is acrylonitrile, cannot be satisfactorily dyed by standard dyeing processes. One standard process for dyeing textile materials is the so-called naphthol dyeing process described for example, in "American Dyestuii Reporter, vol. 28 (1939), pages '79 to 84 inclusive. However, this process, when applied according to known technique, is not effective to produce even shades on articles composed of acrylonitrile polymers of the type referred to herein. Thus, when the standard naphthol dyeing process is applied to yarns and filaments of acrylonitrile polymers, the dyeing is very spotty and uneven and occurs mainly at out ends of the filaments.

Since this invention is of most particular interest when applied to yarns composed oi polyacrylonitrile, the invention will be described most specifically with respect to polyacrylonitrile yarns, but it will be understood that it is broadly applicable to articles, and the like, composed of acrylonltrile polymers, including copolymers and interpolymers, and particularly those polymers in which at least 85% by weight of the polymer is the acrylonitrile unit which is considered to be present in the polymer molecule as i. e., at least 85% by weight of the reactant material'converted into and forming the polymer is acrylonitrile.

One object of this invention is to effect a uniform dyeing or articles composed of acrylonitrile polymers. A further object of the invention is to eflect the uniform dyeing of yarns composed of the acrylonitrile polymers in which at least by weight of the polymer is acrylonitrile. A further object is concerned with polyacrylonitrile yarn which is dyed deeply and uniformly and in which the dye is fast to light and washing. Other objects will appear hereinafter.

The objects of the invention are accomplished in general by treating a gel polyacry onitrile yarn in a bath containing a naphthol first component, squeezing excess bath from the yarn, immersing the yarn in an aqueous solution of acid, rinsing the yarn in water to remove the particularly yarns, filaments Example I A skein of polyacrylonitrile yarn in the gel state was immersed for one half hour at room temperature (25 C.) in a bath made up as follows: 1.6 grams oi the anilide of beta-oxynaphthoic acid were mixed with 4 m1. of ethyl alcohol and dissolved by the addition of 1.2 ml. of 25% aqueous sodium hydroxide and 3 ml. 01' water. The solution was poured into approximately 150 ml. 01' water containing 1.8 ml. of 25% aqueous sodium hydroxide and 4 cc. 01' 10% aqueous dispersion of the sodium salt of tri-isopropyl naphthalene beta-sulionic acid and the whole diluted to 200 ml. with water. The excess prepared bath was squeezed out of the skein and the skein was then immersed in 10% aqueous sulfuric acid solution for one to three minutes. The skein was then rinsed in tap water and immersed overnight in a coupling bath prepared by dissolving 4 grams of stabilized diazo salt prepared from 2.5-dichloroaniline in 200 ml. 01' water containing 6 grams of sodium chloride. The yarn was dyed by this procedure to a strong, level shade which was fast to light and washing.

If the acid treatment 01' the prepared yarn was omitted in the above example, the yarn was dyed only at a cut end or spottily throughout the skein, resulting in a completely unsatisfactory dyeing.

Example II t'mmple III Using the same gel yarn and procedure of Example I except that 2 N aqueous acetic acid was used for the acid dip instead of 10% aqueous sulfuric acid solution, like results were obtained.

3 Example IV Using the same gel yarn and procedure of Example I except that 0.5 N aqueous acetic acid was used for the acid dip instead of aqueous sulfuric acid solution, like results were obtained.

Example V Using the same gel yarn and procedure used in Example I, but substituting in place of the anilide of beta-oxynaphthoic acid and stabilized diazo salt prepared from 2,5-dichloroaniline, the components listed below in a series of four experiments, strong, level dyeings were obtained:

' Example VI The same gel yarn used in Example I was treated, prior to the treatment of Example I, for thirty minutes at 50 C. with an aqueous solution containing 2.5% hydrogen peroxide and 0.5% sodium hydroxide, the yarn thus being partially hydrolyzed with respect to the nitrile groups of the polymer and being highly bleached by the hydrogen peroxide. After rinsing and drying, the dried yarn was then subjected to the same procedure applied in Example I to gel yam with strong, level dyeing resulting. As in the other examples, it the acid dip is omitted spotty dyeing results. This example illustrates the application of the dyeing process of the invention to a dried yarn, as contrasted with the gel yarn treatments of the preceding examples.

Example VII Using the same gel yarn and procedure as in Example I except that coupling was carried on at 50 to 60 C. for one half hour instead of overnight, the dyeing is fully as level and strong as in Example 1.

Example VIII By using the same yarn and procedure as in Example I, but substituting 2 N aqueous formic acid instead of 10% aqueous sulfuric acid and immersing the skein therein for thirty seconds at 35 0., strong, level dyelngs equal to those of Example I were obtained.

' The above examples illustrate the obtaining not only of level shades, but also of deep or strong shades. The elimination of the acid dip results in spotty dyeing with the yarn being dyed deeply. in the main, only at the cut ends of the filaments. In order to get even or level dyeing, it is believed necessary to so treat the yarn that its surface skin which, without special treatment, is almost impenetrable to the dye components liquids is made penetrable by a phenomenon which appears to be a desealing" or opening up of the surface skin of the filaments. The following example illustrates dyeing to produce level shades which are not as deep or as strong as those of the previous examples.

Emmplz IX By using the same gel yarn and rocedure of Example I, but substituting 0.5 N and 2.0 N aqueous boric acid solutions respectively at temperatures of 25 C. and 50 C. respectively in place of the sulfuric acid dip of Example I, level dyeing which is not as deep as that obtained through Example I results.

The dye components referred to in the preceding examples are identified in the article from American Dyestuff Reporter, referred to above. The dye component first used in the examples is designated as naphthol first component and is used in an alkaline medium and the component which couples therewith is designated as a diazotized naphthol base," for convenience. It will be understood, as stated in the said article from the "American Dyestufl Reporter, that the second components. 1. e., the diazotized naphthol bases, are preferably used in the form of their salts, e. g., the hydrochloride. The diazotized naphthol base may be used in the form of the commercially available stabilized salt which is dissolved as desired to form the coupling bath, but it may be used in the form of the solution in which the diazo naphthol salt is formed, e. g., by diazotizing the naphthol base in suitable acid medium such as dilute hydrochloric acid. Any combination of naphthol first component and diazotized naphthol base which will combine to form a dyestufl as pointed out in the said article in American Dyestufi Reporter, can be used in the practice of the invention.

The acrylonitrile polymer for use with this invention is preferably prepared by the ammonium persulfate catalyzed polymerization of monomeric acrylonitrile d ssolved or emulsified in water. It can however be prepared by any other suitable type of polymerization reaction, such as for example the emulsion type reaction disclosed by U. S. Patent No. 2,160,054 to Bauer et al. The polymer preferably possesses a. molecular weight within the range 15,000 to 250,000 or even higher, as calculated from viscosity measurements by the Staudinger equation:

Molecular weight C=concentration of the solution expressed as the number of moles of the monomer (calculated) per liter of solution.

The molecular weight of the polymer obtained is dependent on such factors as the concentration of the monomer in the water, the amount and type of catalyst present, the temperature of the reaction, etc. When the monomer is present in 5% aqueous solution maintained at a temperature of from 3 to 5 C., it is found that the use of 4% ammonium persulfate catalyst (based on the weight of the acrylonitrile) results in the formation of a polymer having a molecular weight (as calculated by the above equation) of approximately 60,000. Increasing or decreasing the amount of the catalyst, while maintaining the other conditions constant, decreases or increases the molecular weight of the polymer. Acrylonitrile copolymers and interpolymers containing at least by weight of acrylonitrile and likewise preferably having a molecular weight of 15,000 to 250,000 or higher, can be prepared in a similar manner. The spinning solution usually has a vislar weight of the polymer until the glycerol cosity of 25 to 750 poises and the average molecu- 40,000 and 150,000 to spinning solution tioned.

The polyacrylonitrile produce a to 25% within the viscosity range menyarn used in the above examples was prepared by the so-called "wet" spinning process and can be produced according to the following procedure:

A solution of 18 parts of polyacrylonitrile possessing an average molecular we ght of 120,000,

N as determined from viscosity measurements by the Staudinger formula, in 82 parts of dimethyl formamide is extruded at a temperature of 100 C. through a ten-hole spinneret into a spinning bath consisting of glycerol heated to a temperature of 140 C., the solution being extruded at a Jet velocity of 4'70 inches per minute. The yarn is led through the bath for a distance of 24 inches, being subjected during its travel through the bath to a tension of 1.2 grams per denier by means of a snubbing tension guide comprising two stationary pins mounted at a distance of 16 inches from the spinneret face. the yarn is passed without slippage about a positively driven feed wheel possessing a peripheral speed of 3.600 inches per minute, the yarn be- On leaving the bath,

Where skeined yarn into skeins from the in running water may, if desired, be liqu d. for example water and other liquids which can be used as coagulating bath liquids for acrylonitrile polymers, but the yarn should not lose its swollen condition prior to the treatment of this invention in order that it may be maintained in the gel state. The removal of glycerol from the yarn by washing with water is an inexpensive and preferred expedient to remove from the yarn relatively non-volatile .materials present in the coagulating bath.

The time consumed by the various steps of the process is not particularly critical, liquid treatments as set forth herein being maintained for a period suificient to elect adequate penetration of the filaments by the treatment liquids. As is evident from the examples, the'temperatures of treatment can be varied and the liquid treatments will normally be carried out within the range of about to 60 0., for example at room temperature.

The wetting agent described in Example I,

will be between about a0 scope of the claims.

namely sodium tri-isopropyl naphthalene sulfonate can be replaced by other wetting agents known to the art in the preparation of the naphthol first component bath.

' As illustrated above. the yarn may be treated with a bleaching agent such as hydrogen peroxide or sodium hypochlorite solution to eflect color removal prior to treatment by this invention, if desired.

It is preferred that the acid dip treatment be efl'ected by the use of aqueous solutions of acids, both organic and inorganic. having an ionization constant (Ka) of about 2x 10- or greater; the concentration of acid in the aqueous solution may vary within relatively wide limits, but it is preferred that concentrations be in the ne ghborhood of 3 N or less, preferably about 1 N to 2 N. Where level but weaker dyeings are desired, somewhat weaker acids may be used, e. g., acids having a Ka of 2x10 to 1x10-".

While the invention is of the greatest benefit when applied to the treatment of acrylonitrile polymer yarns, it will be understood that it may be likewise applied with corresponding benefit to the dyeing of other articles composed of acrylonitrile polymers, for example staple fibers, monofilaments, films, tubing and the like.

Any modification of the procedure described herein which conforms to the principles of-the invention is intended to be included within the I claim:

1. The process of dyeing an article composed of acrylonitrile polymer which comprises treating such article witha naphthol first component, subjecting the treated article to an aqueous acid solution and thereafter app ing to the article a diazotized naphthol base coupling component for said first component.

2. The process of dyeing a gel article composed of acrylonitrile polymer which comprisestreating such article with a naphthol first component, subjecting the treated article to an aqueous acid solution and thereafter applying thereto a diazotized naphthol base coupling component for said first component.

3. The process of dyeing gel yarn composed of'acrylonitrile polymer which comprises treating such yarn with a naphthol first component, subjecting thetreated yarn to an aqueous acid solution and thereafter app ying to the yarn a diazotized naphthol base coupling component for said first component.

4. The process of dyein gel yarn composed of acrylonitrile polymer which comprises treating such yarn with a naphthol first component, subjecting the treated yarn to an aqueous solution of an acid having an ionization constant not less than.2x10-', and thereafter applying to the yarn a diazotized naphthol base coupling component for said first component.

FRANK BALDWIN MOODY.

REFERENCES crrnn The following references are of record the file of this paten UNITED STATES PATENTS Name Oct.8.1940

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